Constant velocity joints have a boot mounted thereon to prevent grease sealed therein from leaking into the outside and to prevent foreign matter from intruding into the constant velocity joint. This boot is generally composed of a large end side attaching section adapted to be mounted on a boot attaching section provided at the end of the outer joint member of the constant velocity joint, a small end side attaching section adapted to be mounted on boot attaching section provided on a shaft linked to the constant velocity joint, and a bendable section for integrally linking the two attaching sections. Constant velocity joint boots which are in wide use include one molded of rubber such as chloroprene, and another molded of thermoplastic elastomer.
On the other hand, there are a variety of constant velocity joints including a fixed type constant velocity joint capable of taking a large working angle θ of about 45-50 degrees (Rzeppa type and Birfield type), and a plunging type constant velocity joint having a mechanism which, though not capable of taking so large a working angle, is capable of sliding axially of the outer joint member (double offset type, tripod type, cross groove type). The shape of the outer joint member is varied; the contour of its opening is cylindrical in one type and non-cylindrical in another type. There are many cases where it is more effective to apply the non-cylindrical type from the aspects of weight reduction and processability. As for such boots applied to non-cylindrical outer joint members, chloroprene rubber boots have been used.
Nowadays application of thermoplastic elastomer boots is being investigated (Japanese Unexamined Patent Publication 10-110738, Japanese Unexamined Patent Publication 10-196673, Japanese Unexamined Patent Publication 2002-13546, Japanese Unexamined Patent Publication 2003-194093, Japanese Unexamined Patent Publication 2003-329057).    [Patent Document 1] Japanese Unexamined Patent Publication 10-110738    [Patent Document 2] Japanese Unexamined Patent Publication 10-196673    [Patent Document 3] Japanese Unexamined Patent Publication 2002-13546    [Patent Document 4] Japanese Unexamined Patent Publication 2003-194093    [Patent Document 5] Japanese Unexamined Patent Publication 2003-329057)